SOLUTION: what are the positive and negative roots of f(x)=x^2+4x-5

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Question 332156: what are the positive and negative roots of f(x)=x^2+4x-5
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E2+%2B+4x+-+5+=+0
Complete the square
x%5E2+%2B+4x+%2B+%284%2F2%29%5E2+=+5+%2B+%284%2F2%29%5E2
x%5E2+%2B+4x+%2B+4+=+5+%2B+4
%28x+%2B+2%29%5E2+=+3%5E2
x+%2B+2+=+3
x+=+1
and
x+%2B+2+=+-3
x+=+-5
The roots are 1 and -5
Here's a plot:
+graph%28+500%2C+500%2C+-10%2C+5%2C+-10%2C+10%2C+x%5E2+%2B+4x+-+5%29+